I have to agree almost 100% with SEALBoy on this one. I think the scale of 1-10 works quite well (granted reviewers are unbiased, and that's hard to do). I read something that I really liked from (I think) Greg Kasavin of Gamespot at the time; he said that their average score is a 7 because, in general, games are good. A 7 (or 70%) in school is a C, which is considered "average." I like this scale because I completely agree. Heck, a game has to get at least a few points just for being able to run on someone's computer or console.
And on the issue of Gamespot or whoever being owned by Cnet - I actually prefer Gamespot to most other rating sites. I couldn't care less how they operate, because I compare the scores I would give to games to the scores Gamespot gives them, and I generally agree. There are definitely anomalies, like Assassin's Creed (holy crap, a freaking 9.0???? That game kind of sucked!), Halo 3 (I would give it an 8.0 or 8.3), GTA 4 (self-explanatory), or some underrated games like Titan Quest. I'd give Titan Quest atleast an 8.5, and I even sacreligiously like it better than Diablo, but sites docked it craploads of points for lack of originality. However, these outliers set aside, I generally agree with their scores. Therefore I go to look at the scores they put out and usually know whether or not I'll like a game based on their score AND review.